Method of sequestering carbon dioxide with spiral fertilization

ABSTRACT

A method of sequestering carbon dioxide (CO 2 ) in an ocean comprises testing an area of the surface of a deep open ocean in order to determine both the nutrients that are missing and the diffusion coefficient, applying to the area in a spiral pattern a first fertilizer that comprises a missing nutrient, and measuring the amount of carbon dioxide that has been sequestered. The application of the first fertilizer in a spiral pattern results in a patch of fertilizer where the concentration of the fertilizer does not vary by more than about 50% within two days of the local application. The concentration of the fertilizer at the center of the patch does not decrease through diffusion by more than about 5% during a time period of about 20 days after the application of the patch of fertilizer. The method may further comprise applying additional fertilizers, and reporting the amount of carbon dioxide sequestered. The method preferably includes applying a fertilizer in pulses. Each fertilizer releases each nutrient over time in the photic zone and in a form that does not precipitate.

BACKGROUND OF THE INVENTION

The field of the invention is controlling the amount of carbon dioxide(CO₂) in the atmosphere. This may have a significant effect on globalclimate change, including global warming.

The carbon dioxide content of the atmosphere has been increasing. Thisis based on measurements over the last 40 years or more. There isconcern that this increase may result in global climate change, whichover time may have an adverse effect on weather, sea level and humansurvival.

This concern has lead to the 1992 Rio Treaty and the Kyoto Protocol of1997. These call for significant decrease in the amount of carbondioxide released to the atmosphere from the burning of fossil fuels bythe industrial world. If these reductions are put into effect, thenserious adverse consequences are expected. The economy of theindustrialized world could be significantly, adversely affected. Thiscould result in a loss of jobs, decreases in the standard of living,reduction in life span and possible political unrest. Moreover, thiswould not be a solution because it does not permit or require a reversalof the currently increasing levels of carbon dioxide in the atmosphere.

Carbon dioxide is released into the atmosphere both by the burning offossil fuels, and by the recycling of plant materials. Carbon dioxide isremoved from the atmosphere by the photosynthesis of plants on land andin the oceans. This removal of carbon dioxide from the atmosphere may bereferred to as a carbon dioxide sink. It is the net flow (releases minussinks) that has caused the increase in atmospheric carbon dioxide levelwhich is of present concern. Without human intervention, the net flow ofcarbon dioxide into and out of the atmosphere is roughly zero, with thesources and sinks in rough balance. When fossil fuels are burned, onlyabout 60 percent of the released carbon dioxide is subsequently takenout of the atmosphere by natural sinks. The remaining about 40 percentincreases the carbon dioxide level of the atmosphere, leading to concernover climate changes.

The net carbon dioxide released into the atmosphere can be reduced, butnot eliminated, by increasing the efficiency of power-producingequipment and by harnessing wind and solar power. Generally speaking,these approaches are costly and may be reaching their practical limits.We have been increasing the efficiency of heat engines for over 200years, and may be approaching the limits of basic thermodynamics. It isvery costly to harness low intensity power sources such as wind, waves,sunlight and ocean thermal gradients, especially where energyrequirements are large. Moreover, these approaches can only reduce theincrease in carbon dioxide concentration, never eliminate the increase.Therefore, these approaches cannot adequately address the concern overthe increasing carbon dioxide content of the atmosphere.

The technology of carbon dioxide sink enhancement is in its infancy. Thesequestering of carbon dioxide in geological formations is bothbeneficial and inexpensive, if the carbon dioxide is relativelyconcentrated. An example of relatively concentrated carbon dioxide isthe off-gas after removal of methane from natural gas containing carbondioxide. However, there is relatively little carbon dioxide available insuch concentrated form. Most carbon dioxide is available inconcentrations of from about 10 percent to about 25 percent in exhaustgases from the combustion of fossil fuels. It is quite expensive toincrease the concentration of carbon dioxide from about 10 or 25 percentto about 100 percent. The preferable course of action appears to be theuse of sunlight and plants to do the concentrating, and subsequently tosequester the resulting plant material in some manner.

One approach would be to plant trees. However, there is not enough landto plant sufficient trees to zero out the net carbon dioxide production.Even if there were enough land, we would have to find a place to storethe resulting wood after about 50 to about 100 years, such that the woodwould not rot and release carbon dioxide to the atmosphere. Thus, thisapproach would not sequester carbon dioxide for a relatively long periodof time.

The best place to enhance plant growth is in the oceans. Ninety-eightpercent of the surface of the ocean is a barren desert with almost noplant life. About sixty percent of the plant life (phytoplankton) in theoceans of the world arises from about only two percent of the surface ofthe oceans. A reduction in the net flow of carbon dioxide may beachieved, if some of that ninety-eight percent of the surface of theocean is made as productive as that two percent.

SUMMARY OF THE INVENTION

A method of sequestering carbon dioxide comprises the following steps:testing an area of the surface of an ocean for suitability; fertilizinga suitable area of the surface of the ocean to increase plant life andsequester carbon dioxide; and measuring the amount of carbon dioxidethat has been sequestered. The testing includes a determination of thediffusion coefficient in the surface of the ocean so that an optimumpattern of fertilization can be designed. The fertilizing preferablyincludes a ship dispersing liquid fertilizer in a spiral pattern whichstarts at the center of the spiral that is marked by a buoy that floatswith the current. The method may include the additional step ofreporting the amount of carbon dioxide that has been sequestered. Anarea of the surface of an ocean is suitable if both at least onenutrient is missing to a significant extent, and the water is deep. Anutrient is missing to a significant extent, if the metabolism of carbondioxide is reduced to a significant extent by the level of the nutrientin the water. An appropriate amount of a missing nutrient is an amountto raise the concentration of the nutrient at the ocean surface so thatthe metabolism of carbon dioxide is no longer reduced to a significantextent by the concentration of the nutrient. The depth of the water ispreferable at least about 5,000 feet (about 1524 meters), morepreferably at least about 10,000 feet (about 3048 meters), and mostpreferably at least about 15,000 feet (about 4572 meters). Thefertilizing creates a new verdant zone, preferably in the ocean surfaceabove very deep water. The testing and reporting may be carried out byany of a number of methods that are known to one of ordinary skill inthe art. The reporting may be carried out in a number of forms.Conventional forms would include printing the report on paper or anothersubstrate, or storing the report in magnetic media or optical media. Thereport may be in a form required by a governmental authority. Suchgovernmental authority may monitor the amount of carbon dioxide that isreleased into the atmosphere by a particular person or company. Theamount of carbon dioxide released may be a debit on the balance sheet ofsuch person or company. The governmental authority may allow credits onsuch balance sheet for the amount of carbon dioxide stated in suchreport as being sequestered.

DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic illustration of a spiral pattern of fertilizationaccording to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The testing of an area of the surface of an ocean for suitability forthe present method preferably includes a determination of the diffusioncoefficient for the surface of the water. This allows for an estimate tobe made of the mixing of the fertilizer that will take place over afixed period of time after the application of the fertilizer. In orderto make this estimate, one also needs to know the composition of thefertilizer. In a preferred embodiment, the diffusion coefficient ismeasured using the same liquid or pelletized fertilizer that will beapplied to the surface of the ocean.

The fertilizing of a suitable area of the surface of the ocean toincrease plant life and sequester carbon dioxide, preferably includesthe application of a pelletized, liquid or powdered fertilizer in aspiral pattern to create a patch of fertilizer. Preferably, the size ofthe patch of fertilizer is such that the center of the patch is notdisturbed by the edges of the patch for at least about twenty days afterthe fertilizer is applied. In a preferred embodiment, the concentrationof the fertilizer in the center of the patch does not decrease throughdiffusion by more than about 5% during a time period of about twentydays after the patch is applied, which may define the minimum size ofthe patch of fertilizer.

The size of the patch of fertilizer is also affected by other factors.The vessel that applies the fertilizer may be a ship that is capable ofa speed of about 15 to about 18 knots. Multiple vessels may be used. Ina preferred embodiment, a single ship applies the patch of fertilizerover a time period of from about 3 to about 4 days. The maximum size ofthe patch may be affected by the top speed of the vessel, the maximumrate at which the vessel can distribute the fertilizer, and theconcentration of the nutrients in the fertilizer. Preferably, a liquidfertilizer is used which may allow the rate at which the fertilizer ispumped into the ocean to be more precisely controlled in relation to thespeed of the vessel.

FIG. 1 shows a schematic view of a preferred pattern of application ofthe fertilizer. The center 1 of the spiral may be defined by theplacement of a floating buoy. The buoy may be carried by the current.Thus, the latitude and longitude of the center of the spiral may vary asthe fertilizer is applied. The vessel may begin applying the fertilizerat the center 1 of the spiral, and continue application of thefertilizer in the spiral pattern as shown by line 8 which ends at point9. The fertilizer is applied such that the concentration of thefertilizer in the surface of the ocean does not vary by more than about50% between the arms of the spiral within from about one to about twodays after the fertilizer is applied. A radius is shown in broken lineconnecting the center 1 with points 2, 3, 4, 5, 6 and 7 on line 8. Theconcentration of the fertilizer may be at a maximum at points 1, 2, 3,4, 5, 6 and 7. The concentration of the fertilizer may be at a minimumat the points along the radius which are equidistant from points 1 and2, equidistant from points 2 and 3, equidistant from points 3 and 4,equidistant from points 4 and 5, equidistant from points 5 and 6, andequidistant from points 6 and 7. In a preferred embodiment, theconcentration at each of these equidistant points is no less than about50% of the concentration of each of points 1, 2, 3, 4, 5, 6 and 7.Within a time period of from about 1 to about 2 days after completion ofthe application of the patch of fertilizer, the concentration of thefertilizer over the entire surface of the patch may be from about 50% toabout 60% of the maximum concentration of the fertilizer at any point inthe patch due to the mixing of the fertilizer in the surface of theocean.

The spiral application of the fertilizer preferably results in acontinuous bloom of phytoplankton across the entire surface of the patchof fertilizer, and does not result in dots of blooms or overfertilization. This may allow for the maximum fixation of carbon withinthe interior of the bloom. The center of the patch may be regarded asthat area which is sufficiently distant from the edge of the patch, sothat the variation of the concentration of fertilizer there is due onlyto the initial concentration and the utilization of the fertilizer bythe phytoplankton bloom.

Sequestration of carbon dioxide by fertilizing a suitable area of thesurface of an open ocean has a number of benefits. Substantial amountsof carbon dioxide may be sequestered for substantial periods of time.The present invention may sequester all of the net carbon dioxideproduced by the burning of fossil fuels because about 53 percent of thecarbon taken out of the ocean (and from the atmosphere) by the processof the present invention is expected to be sequestered in the deep oceanfor about 1,000 to about 2,000 years, as has been measured in the deep,tropical Pacific Ocean. The present invention should not be carried outin a shallow bay or lake because this could produce anoxic conditions.

The barren ocean may be made verdant by adding the missing nutrients tothe ocean surface. This occurs naturally in the upwelling off of Peruwhere nutrient-rich bottom water comes to the surface and thephytoplankton bloom.

Whether an area of the surface of an ocean is suitable for sequesteringcarbon dioxide depends on a number of factors. The depth of the oceanshould be sufficient to prevent the development of anoxic conditionsafter fertilization. The depth of the thermocline, about 50 to 300 ft.(about 15 to 91 meters), is preferably less than the depth of the photiczone, such that the thermocline prevents the fertilizer from reaching adepth below the photic zone. The photic zone extends from the surface ofthe ocean to a depth of from about 150 to 300 feet (about 46 to 91meters), generally speaking. The photic zone may best be describedfunctionally. It extends from the surface to a depth where sunlight nolonger causes an appreciable amount of photosynthesis. However, if thedepth of the thermocline is greater than the depth of the photic zone,then the fertilizer may comprise a float material to prevent thefertilizer from sinking to a depth below the photic zone. The amount andnature of the fertilizer depends on the nutrients that are missing fromthe surface of the ocean. Preferably, iron is the only nutrient that ismissing to a significant extent from the area of the ocean to befertilized. This allows fertilization with a fertilizer that comprisesonly iron salts, and preferably iron chelates that prevent the iron fromprecipitating to any significant extent. The preferred chelates includelignin, and particularly lignin acid sulfonate. However, other nutrientsmay be missing from the surface of the ocean. If nitrogen is missing toa significant extent, then the fertilizer may comprise at least onenutrient which causes bloom of at least one microorganism that fixesnitrogen. The microorganism may be from the group consisting of bluegreen algae and phytoplankton. The surface of the ocean may also bemissing phosphate and trace minerals, which may be incorporated into thefertilizer system. If the surface of the ocean is missing both iron andan additional nutrient, then the preferred method may include theseparate application of a plurality of fertilizers. The first fertilizerpreferably includes iron, and more preferably an iron chelate. The othermissing nutrients may be applied in a second fertilizer, or in aplurality of additional fertilizers. It is preferred that eachfertilizer release the corresponding nutrient in a form that does notreact with any iron chelates in the first fertilizer and that does notprecipitate to any substantial extent.

The amount of carbon dioxide that is sequestered by carrying out afertilization according to the present invention depends upon a numberof factors. The composition, amount and rate of distribution of thefertilizer are all factors. The nutrient content of the water of theocean is also a factor, not only at the location of the application ofthe fertilizer, but also all locations to which the fertilized water issubsequently carried by any currents. The temperature, the amount ofsunlight and the depth of the thermocline are factors. The nature andnumber of the organisms in the water that metabolize the fertilizer orthat eat the plant materials produced, are also factors.

The primary missing nutrient is iron in much of the surface of theoceans. In an experiment, iron salts were added to a portion of thesurface of the barren tropical Pacific ocean. A bloom of phytoplanktonresulted. This plant bloom turned the ocean from deep blue to milkygreen and drew down the carbon dioxide concentration in the fertilizedwater. The phytoplankton increased about 27 times versus background inabout nine days, as a result of fertilization with iron salts during thefirst, fourth and eighth days (days zero, three and seven of theexperiment). This plant bloom occurred in spite of the relatively lowefficiency of the fertilizer that was used (about 95 percent of the ironprecipitated out of the photic zone shortly after application).

A test has been carried out to evaluate the application of fertilizersthat comprise both iron and phosphate. The initial fertilizationproduced a bloom of phytoplankton of about 4.5 to 7 times the initialconcentration of such phytoplankton, in just over one day. Adverseweather and ocean conditions after the first day precluded furthereffective measurements.

A second test has been carried out to evaluate the application of aniron fertilizer. Iron-containing pellets were dispersed over a ninesquare mile patch of open ocean. This resulted in an increase ofphytoplankton concentration of about five times the backgroundconcentration of phytoplankton. The maximum bloom appeared to be about600 pounds of phytoplankton per pound of fertilizer, by extrapolatingover the increasing size of the patch at nearly constant phytoplanktonconcentration.

The measurement of the amount of carbon dioxide that is sequestered bycarrying out the fertilization of the present invention may require thatsome estimates be made. Total dissolved carbon may be removed from thewater at the surface of the ocean by three mechanisms: (1) some will goto the bottom of the ocean as sinking organic particles; (2) some willbe dispersed by currents; and (3) some will be degassed to theatmosphere over the ocean. Numerous organisms may metabolize eachnutrient including inorganic nitrogen that is available at the surfaceof the ocean. These organisms may be removed from that area of thesurface of the ocean by two mechanisms: (1) some will go to the bottomof the ocean as sinking organic particles; and (2) some are dispersed bythe current or swimming. None are removed to the air over the ocean. Asthese phytoplankton organisms metabolize each fertilizer, they usuallyuptake both carbon in the form of carbon dioxide and nitrogen in theform of nitrates. Estimates may be made of the amount of organic carbonthat sinks to the bottom of the ocean by assuming that the amount oforganic carbon that sinks to the bottom of the ocean is proportional tothe amount of organic nitrogen that sinks to the bottom of the ocean.The amount of organic nitrogen that sinks to the bottom of the ocean canbe measured from the draw down of inorganic nitrates and thecarbon-nitrogen ratios in the organic materials formed. As the particlesof organic carbon sink below the main thermocline, this organic carbonis effectively sequestered in the deep ocean for periods of timeapproaching the time scale of organic turnover which is from about 1,000to about 10,000 years.

The present invention allows for the sequestration of substantialamounts of carbon dioxide. Preliminary calculations indicate that foreach year, for each eight square miles of deep tropical oceanfertilized, about 17,000 tons of carbon dioxide containing about 4,600tons of carbon may be converted to biomass and sequestered to the oceanfloor. After a substantial period of time such as over about the next1,000 to 2,000 years, most of this carbon is expected to be oxidized tocarbon dioxide and returned to the surface of the ocean in the form ofsuper-saturated ocean upwellings but a part will remain in the deepocean in the form of calcium carbonate and other carbonaceous materials.Therefore, the present invention may sequester the 40 percent of thecarbon dioxide that the U.S. produces by burning fossil fuels each yearand that is not taken out by natural sinks, if this continuousfertilization is carried out over 1,100,000 square miles of deep barrenocean surface. The estimated current cost is about $5 per ton of carbonsequestered, when one considers that about 1,000 tons of carbon will besequestered per ton of fertilizer spread over the surface of the deepbarren ocean. This estimated cost is much lower than the estimated costof alternative approaches primarily because of the use of sunlight toconcentrate the carbon dioxide from the ocean surface and the atmosphereinto the form of biomass which is then sequestered naturally over longperiods of time.

There are additional consequences of carrying out the method of thepresent invention. About half the biomass that is created byfertilization according to the present invention will be recycledthrough zooplankton, fish and marine mammals. If there is continuousfertilization according to the present invention of about 1,100,000square miles of deep barren ocean, then it is estimated that anadditional 70 million tons of catchable fish per year would be produced,or about two-thirds of the current world fish production. This is basedon an estimate of 60 tons of catchable fish per square mile per yearunder continuous fertilization. These estimates may be subject torevision because there are many variables as one moves up the food chainfrom the phytoplankton. These variables are not particularly wellunderstood or easy to control at this time. However, it is known thatwhere this fertilization occurs naturally, such as off of Peru, theocean is able to take advantage of the available food and produce abloom of fish. The amount of catchable fish per year per square mile ofbarren ocean that is fertilized, may be increased by seeding the oceanwith filter-feeder fish. The introduction of these fish will increasethe fraction of biological carbon that is recycled to the atmosphere ascarbon dioxide, and will decrease the fraction that is sequestered tothe ocean depths. Therefore, carbon dioxide sequestration is preferablycarried out with fertilization pulses of less than thirty days in aparticular body of water, to limit the zooplankton and fish growth. Theuse of fertilization pulses can increase sequestration of carbon dioxidefrom as little as ten percent of organic carbon formed to as much aseighty percent organic carbon formed. The length of such a fertilizationpulse is more preferably less than about twenty days in a particulararea. The time period between fertilization pulses in a particular areais preferably in excess of about thirty days, and more preferably inexcess of about forty-five days from the end of one pulse to thebeginning of the next pulse.

The environmental effects of carrying out the method of the presentinvention are expected to be benign, because the same fertilization hasbeen going on naturally in upwellings for millions of years. The maineffect of carrying out the method of the present invention is expectedto be substantial increases in the food supplies of, and therefore thepopulation of zooplankton and fish in the newly created verdantecosystems. Preferably, the fertilization according to the presentinvention will not take place near living coral reefs or in shallowwater, so as to avoid any adverse effect thereon. In any event, theenvironmental effects at the ocean surface of carrying out the presentinvention will be short term, vanishing within about one month from thecessation of fertilization. If at some time in the future it is decidedto carry out such fertilization on a large scale as part of a method ofocean farming, then the carbon dioxide content of the atmosphere mayindeed be significantly reduced and, therefore, the possibleenvironmental effects of such large scale ocean farming should becarefully monitored as large scale ocean farming is implemented.

The ocean fertilization of about 1,100,000 square miles (about 3,000,000square kilometers) at a rate of removing about 2 billion tons (about 1.8billion metric tons) of carbon dioxide (CO₂) would initially requireabout 700,000 tons (about 644,000 metric tons) per year of fertilizerand would sequester the net annual carbon dioxide production of theUnited States from burning fossil fuels. This is about 2,000 tons (about1,800 metric tons) per day for 350 days per year. If the fertilizerapplied to the ocean costs about $5000 per ton (about 0.9 metric ton),then the cost is about $3.5 billion per year. This cost includes thecost of monitoring, testing and reporting, so as to optimize the methodof sequestration, including the optimization of the composition of thefertilizer, the application rate and the location of application.

Thus, the present method allows for variation, including variation inthe composition of the fertilizer, as well as the location and nature ofthe application of fertilizer, depending on a number of factors.

A method of sequestering carbon dioxide is disclosed by U.S. patentapplication Ser. No. 09/304,063, which is hereby incorporated byreference. Methods of increasing seafood production in the ocean aredisclosed by U.S. Pat. Nos. 5,433,173, 5,535,701, and 5,967,087, whichare hereby incorporated by reference.

Variations of the invention may be envisioned by those skilled in theart and the invention is to be limited solely by the claims appendedhereto.

I claim:
 1. A method of sequestering carbon dioxide in a deep open oceancomprising the following steps: (1) testing an area of the surface of adeep open ocean, in order to confirm that at least a first nutrient ismissing to a significant extent from said area, and to identify saidfirst missing nutrient; and (2) applying in a spiral pattern to saidarea a first fertilizer which comprises said first missing nutrient, tofertilize said area with an appropriate amount of said first missingnutrient whereby carbon dioxide is sequestered; and (3) measuring theamount of sequestered carbon dioxide that results from saidfertilization of said area.
 2. The method of claim 1, wherein saidspiral pattern starts at a buoy that floats with current.
 3. The methodof claim 2, wherein said first fertilizer comprises an iron chelate, andsaid chelate comprises lignin acid sulfonate.
 4. The method of claim 2,wherein said spiral pattern comprises a plurality of arms.
 5. The methodof claim 4, wherein said first fertilizer comprises an iron chelate, andwherein said chelate comprises lignin acid sulfonate.
 6. The method ofclaim 4, wherein the concentration of said first fertilizer in said areadoes not vary by more than about 50% between said arms of said spiralfor from about one to about two days after said applying to said arms.7. The method of claim 1, wherein said testing further comprises adetermination of the diffusion coeffecient of said area.
 8. The methodof claim 1, further comprising the step of limiting zooplankton and fishgrowth in said area by applying said first fertilizer in pulses.
 9. Themethod of claim 8, wherein the time period between end of the precedingpulse and the start of the following pulse is in excess of about thirtydays.
 10. The method of claim 9, wherein said area of the surface ofsaid deep open ocean has a thermocline at a depth of less than about 110meters.
 11. The method of claim 1, wherein said testing furthercomprises testing said area to determine the depth of said open ocean,and wherein said depth is in excess of about 5,000 feet.
 12. The methodof claim 1, further comprising the following step: (4) reporting theamount of sequestered carbon dioxide that results from saidfertilization of said area.
 13. The method of claim 12, wherein saidtesting further comprises a determination that in said area the depth ofthe thermocline is less than the depth of the photic zone.
 14. Themethod of claim 12, wherein said reporting further comprises deliveringa report of the amount of sequestered carbon dioxide, wherein saidreport is fixed in a tangible form selected from printing on asubstrate, or data stored in magnetic or optical media.
 15. The methodof claim 1, wherein said applying is completed over a time period offrom about three to about four days.
 16. The method of claim 1, whereinsaid applying forms a patch of fertilizer, and the minimum concentrationof said first fertilizer at any point in the surface of said patch isnot less than from about 50% to about 60% of the maximum concentrationof said first fertilizer at any point in the surface of said patch at atime about three days after the last application of fertilizer.
 17. Amethod of fertilizing an ocean comprising the following step: applyingin a spiral pattern a first fertilizer to an area of the surface of anocean.
 18. The method of claim 17, wherein said spiral pattern starts ata buoy that floats with current.
 19. The method of claim 17, whereinsaid spiral pattern comprises a plurality of arms, and the concentrationof said first fertilizer in said area does not vary by more than about50% between said arms of said spiral for from about one to about twodays after said applying to said arms.
 20. A report comprising astatement of the amount of carbon dioxide sequestered by a method ofsequestering carbon dioxide in a deep open ocean wherein said methodcomprises the step of applying in a spiral pattern a first fertilizer toan area of the surface of said ocean.